1. Novartis, East Hanover; New Jersy U.S.A.
2. Department of Applied Ecology and Statistics, North Carolina State University, Raleigh; North Carolina U.S.A.
3. Patuxent Wildlife Research Center, USGS, Laurel, Maryland 20708; U.S.A.
4. Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907; U.S.A.